1. Field of the Invention
The present invention relates to a method of manufacturing a thin-film magnetic head having at least an induction-type electromagnetic transducer for write operations.
2. Description of the Related Art
The recording schemes for a magnetic read/write apparatus include a longitudinal magnetic recording scheme which employs the direction of signal magnetization along the surface of the recording medium (or in the longitudinal direction) and a vertical magnetic recording scheme which employs the direction of signal magnetization perpendicular to the surface of the recording medium. When compared with the longitudinal magnetic recording scheme, the vertical magnetic recording scheme is said to be less affected by the thermal fluctuation of a recording medium and therefore possible to implement a higher linear recording density.
In general, the thin-film magnetic head that employs the longitudinal magnetic recording scheme comprises: a medium facing surface (or air bearing surface) that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions that are opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, with a gap layer provided between the pole portions; and a thin-film coil at least a part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers.
On the other hand, examples of the thin-film magnetic head that employs the vertical magnetic recording scheme include a ring head having the same structure as that of the thin-film magnetic head that employs the longitudinal magnetic recording scheme, and a single magnetic pole head for applying a magnetic field in a direction perpendicular to the surface of the recording medium with one main magnetic pole. Generally, for the single magnetic pole head, used as a recording medium is a two-layer medium that has a soft magnetic layer and a magnetic recording layer stacked on a substrate.
With a recent trend toward higher recording density, reduction in track width has been desired for thin-film magnetic heads. In this connection, reduction in the width of a magnetic pole that defines the track width has also been desired for thin-film magnetic heads which operates on either of the longitudinal magnetic recording scheme and the vertical magnetic recording scheme. Conventionally, however, there have been two problems which make it difficult to reduce the width of the main magnetic pole.
A first problem is that it is difficult to pattern the magnetic pole with high accuracy, for example, such that the magnetic pole would have a width of 0.5 μm or less. That is, a magnetic layer including a magnetic pole portion is formed by electroplating (or frame plating), for example, through the use of a resist frame formed by photolithography. However, since the magnetic layer including the magnetic pole portion is formed on a raised portion of an insulating layer that covers the coil, and therefore, the resist frame is formed on the insulating layer that has great differences in height of irregularities. In this case, since the resist cannot be readily formed in a uniform thickness, it is difficult to pattern the resist frame with accuracy. This in turn makes it difficult to accurately pattern the magnetic layer including the magnetic pole portion.
A second problem is that a reduction in width of the magnetic pole causes a magnetic flux to be saturated before the flux reaches the tip of the magnetic pole, thereby causing a reduction in the magnetic field generated from the tip of the magnetic pole in the medium facing surface.
To overcome the aforementioned problems, a thin-film magnetic head for use with the longitudinal magnetic recording scheme often employs a structure in which one magnetic layer is divided into a pole portion layer and a yoke portion layer. The pole portion layer includes a magnetic pole portion exposed in the medium facing surface, and the width of the pole portion layer measured in the medium facing surface defines a track width. The yoke portion layer introduces a magnetic flux into the pole portion layer. If this structure is employed, by forming the pole portion layer to have a saturated magnetic flux density greater than that of the yoke portion layer, it is possible to efficiently introduce the magnetic flux to the tip of the magnetic pole portion, and to form the magnetic pole portion to have a small width. Examples of the thin-film magnetic head having such a structure are disclosed in Published Unexamined Japanese Patent Application (KOKAI) Nos. 11-102506, 2000-57522, and 2000-67413.
Accordingly, it has been proposed for the single magnetic pole heads for use with the vertical magnetic recording scheme, too, to employ such a structure in which the main magnetic pole is divided into the pole portion layer and the yoke portion layer.
In the thin-film magnetic head having the structure in which the magnetic layer for defining a track width is divided into the pole portion layer and the yoke portion layer, it is preferable that the yoke portion layer should have a uniform thickness so as to efficiently introduce a magnetic flux. For that reason, it is preferable to form the yoke portion layer by electroplating. To form the yoke portion layer by electroplating, it is necessary to form an electrode layer on the surface of a base of the yoke portion layer prior to the plating because most of the base is an insulator. In general, a sputtering method is employed to form the electrode layer. After the plating has been carried out, it is necessary to remove an unnecessary portion of the electrode layer that is other than a portion underlying the yoke portion layer.
In general, the yoke portion layer is formed after the pole portion layer has been formed, so as to be connected to the pole portion layer. For this reason, in the case of forming the electrode layer by sputtering, the electrode layer is formed not only on the interface between the pole portion layer and the yoke portion layer but also on a portion of the pole portion layer near the medium facing surface. The electrode layer that has been formed on a portion of the pole portion layer near the medium facing surface is removed after the yoke portion layer has been formed. In this connection, there has been a problem in that when removing the electrode layer, the pole portion layer may deformed or damaged, which can result in deterioration in property.
Moreover, in the case of forming the electrode layer by sputtering, the electrode layer is formed also on both side surfaces of the pole portion layer near the medium facing surface. It is difficult to remove the electrode layer that has been formed on the side surfaces. If part of the electrode layer remains on the side surfaces, a magnetic flux can flow into the recording medium from this part of the electrode layer, too, which can result in an increase in the effective track width, to thereby make it difficult to reduce the track width.